Here’s why owls are dying near marijuana farms

The debate about marijuana legalization is ongoing, but one thing might be for sure. They're killing off owls, according to a new report.

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Researchers from University of California, Davis, and the California Academy of Sciences, recently conducted an experiment, published in the Avian Conservation and Ecology journal, to determine how wildlife inhabits urban or agricultural settings, including illegal marijuana sites.

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To do so, they collected 10 dead spotted owls and 84 dead barred owls from areas in California including Humboldt County, where marijuana farms overlap with owls’ hunting grounds. Seven of the spotted owls and 34 of the barred owl tested positive for anticoagulant rodenticide, a rat poisoning farmers apparently use to keep the rodents away. The substance prevents mammals from recycling vitamin K, which can result in uncontrollable internal bleeding.

Credit: BryanHanson/Morguefile

Credit: BryanHanson/Morguefile

"Spotted owls are inclined to feed along forest edges. Because grow sites break apart these forest landscapes, they are likely source points for exposure," lead study author Mourad Gabriel said in a statement.

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The authors noted that an estimated 4,500 to 15,000 private cultivation sites are in Humboldt County, but only a few permits have been enforced. Therefore, there is no management oversight.

"When you have thousands of unpermitted grows and only a handful of biologists that regulate that for multiple counties, we're deeply concerned that there aren't sufficient conservation protective measures in place," Gabriel said. "If no one is investigating the level at which private marijuana cultivators are placing chemicals out there, the fragmented forest landscapes created by these sites can serve as source points of exposure for owls and other wildlife."

While researchers say more investigations need to be administered to better understand the magnitude of the contamination, they believe their findings are strong.

"We're using our collections,” coauthor Jack Dumbacher said, “to build a concrete scientific case for increased forest monitoring and species protection before it's too late to intervene."

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